Solvated CrBr2(thf)2, a linear chain in the solid state

metal-organic papers

m80

Structure Reports Online

ISSN 1600-5368

Solvated CrBr2(thf)2, a linear chain in the solid state

Brendan Twamley,a_Ralph

Zehnderb_{and Pamela J.}

Shapirob_*

a_{University Research Office, 109 Morrill Hall,} University of Idaho, Moscow, ID 83844-3010, USA, andb_{Department of Chemistry, University} of Idaho, Moscow, ID 83844-2343, USA

Correspondence e-mail: [email protected]

Key indicators

Single-crystal X-ray study

T= 203 K

Mean(C±C) = 0.005 AÊ

Rfactor = 0.027

wRfactor = 0.071

Data-to-parameter ratio = 15.8

For details of how these key indicators were automatically derived from the article, see http://journals.iucr.org/e.

#2001 International Union of Crystallography Printed in Great Britain ± all rights reserved

In the title compound, dibromobis(tetrahydrofuran-O )-chromium(II), [CrBr2(C4H8O)2], CrBr2 is solvated by two

tetrahydrofuran (thf) molecules, with a CrÐO distance of 2.072 (3) AÊ and a CrÐBr distance of 2.5825 (5) AÊ. The Cr atom lies on the center of inversion. The Cr atom is octahedrally coordinated, with the thf CrÐO bond orthogonal to the CrÐBr bond, and the vacant sites are occupied with a Cr Br intermolecular interaction of 2.9874 (5) AÊ. The latter interaction is almost orthogonal to the CrÐO vector. This extends the system into a linear chain along the [100] direction.

Comment

CrBr2(thf)2, (I), bears a close resemblance to the parent

compound CrBr2 (Tracy et al., 1962). Both show slightly

distorted octahedral coordination and both have similar in-plane CrÐBr bond distances, 2.5825 (5) AÊ in (I) and 2.545 (1) AÊ in CrBr2. The solvent molecule, thf in this case,

occupies an in-plane coordination site with a CrÐO distance of 2.072 (3) AÊ. The solvent molecule is coordinated ortho-gonally to the CrÐBr vector with an angle of 90.009 (8)_{. The}

thf molecule is in a half-chair conformation with a total puckering amplitude ofQT= 0.363 AÊ (Cremer & Pople, 1975).

The orientation of the thf molecule is in¯uenced by the intramolecular interactions C4ÐH4A Br1 and C1Ð H1A Br1i_{(see Table 1) which tilt the ring towards each Br}

atom. The out-of-plane coordination site is occupied by an intermolecular Cr1 Br1ii _{interaction of 2.9874 (5) AÊ}

[symmetry code: (ii) 1 +x, y, z]. The corresponding interaction in CrBr2has a Cr Br distance of 2.998 (1) AÊ. The distortion

from ideal octahedral geometry is also re¯ected in the Br1Ð Cr1ÐBr1ii_{angle of 94.65 (2). With the thf molecules}

occu-pying the other coordination sites, (I) can only form a stag-gered chain instead of the planar sheets found in CrBr2. In this

case, the direction of propagation is along [100] (Fig. 1). Other solvent coordinated CrII_Br

2 species that are octahedrally

coordinated show a wide range of CrÐBr distances. The complex CrBr2(CH3CN)2 (Halepotoet al., 1990), which also

forms linear chains, has an in-plane CrÐBr distance of 2.545 AÊ and an out-of-plane distance of 2.976 (1) AÊ. However,

the molecular species trans-CrBr2(pyridine)4 (Holah et al.,

1998) has a CrÐBr bond distance of 2.998 (1) AÊ which indi-cates a very weakly associated Br atom.

Experimental

CrBr2(thf)2was synthesized as a side product during the attempted

synthesis of a chromocene bromide. Tetramethylethylenediyl(5

-bis-cyclopentadienyl)chromoceneII _{carbonyl (331 mg, 1.1 mmol) was}

reacted with 1-bromo-2-methylpropane (155 mg, 1.1 mmol) in tetra-hydrofuran for 20 h at 378 K, with no color change. Dibromomethane (excess) was then added to increase the bromide concentration. Excess solvent and reagents were removed under reduced pressure and the green residue redissolved in tetrahydrofuran (20 ml) and ®ltered. The resulting solution was concentrated to promote crys-tallization and cooled in a 278 K refrigerator overnight. The super-natant was decanted yielding a green crystalline product. The supernatant was concentrated under reduced pressure to yield a ®ne pale green powder. Combined yield 68 mg, 19.1%, m.p. > 573 K.

Crystal data

[CrBr2(C4H8O)2]

Mr= 356.03

Triclinic,P1

a= 4.1043 (7) AÊ

b= 7.4530 (13) AÊ

c= 9.2875 (16) AÊ

= 87.777 (3)

= 78.619 (3)

= 87.281 (3)

V= 278.07 (8) AÊ3

Z= 1

Dx= 2.126 Mg mÿ3

MoKradiation Cell parameters from 839

re¯ections

= 2.2±27.4

= 8.18 mmÿ1

T= 203 (2) K Plate, pale yellow 0.250.200.15 mm

Data collection

Siemens SMART 1000 diffract-ometer

!scans

Absorption correction: empirical (SADABS; Sheldrick, 1999)

Tmin= 0.184,Tmax= 0.293

2917 measured re¯ections 962 independent re¯ections 897 re¯ections withI> 2(I)

Rint= 0.029

max= 25.0

h=ÿ4!4

k=ÿ8!8

l=ÿ11!11

50 frames remeasured standard re¯ections

every beginning and end re¯ec-tions

intensity decay: none

Re®nement

Re®nement onF2

R[F2_{> 2(F}2_{)] = 0.027}

wR(F2_{) = 0.071}

S= 1.08 962 re¯ections 61 parameters

H-atom parameters constrained

w= 1/[2_(F

o2) + (0.0436P)2

+ 0.1523P]

whereP= (Fo2+ 2Fc2)/3

(/)max= 0.001

max= 0.58 e AÊÿ3

min=ÿ0.70 e AÊÿ3

Table 1

Hydrogen-bonding geometry (AÊ,_).

DÐH A DÐH H A D A DÐH A

C4ÐH4A Br1 0.98 2.99 3.599 (4) 122 C1ÐH1A Br1i _{0.98 2.99 3.607 (4) 122}

Symmetry code: (i) 1ÿx;1ÿy;1ÿz.

Data collection:SMART(Bruker, 1997); cell re®nement:SMART; data reduction:SAINT-Plus(Bruker, 1999); program(s) used to solve

structure: SHELXTL (Sheldrick, 1998); program(s) used to re®ne structure:SHELXTL; molecular graphics:SHELXTL; software used to prepare material for publication:SHELXTL.

This work was supported by a grant from the National Science Foundation (CHE-9816730), the DOE EPSCoR Program (Notice 98-02) and the Petroleum Research Foun-dation (ACS-PRF No. 33831-AC). The Bruker (Siemens) SMART CCD diffraction facility was established at the University of Idaho with the assistance of the NSF-EPSCoR program under NSF OSR-9350539 and the M. J. Murdock Charitable Trust, Vancouver, Wa, USA.

References

Bruker (1997).SMART. Version 5.059. Bruker AXS Inc., Madison, Wisconsin, USA.

Bruker (1999).SAINT-Plus.Bruker AXS Inc., Madison, Wisconsin, USA. Cremer, D. & Pople, J. A. (1975).J. Am. Chem. Soc.97, 1354±1358. Halepoto, D. M., Larkworthy, L. F., Povey, D. C., Tucker, B. J. & Smith, G. W.

(1990).J. Chem. Soc. Dalton Trans.pp. 699±701.

Holah, D. G., Hughes, A. N., Lundeen, C. & Magnuson, V. R. (1998).

Polyhedron,17, 2101±2104.

Sheldrick, G. M. (1998).SHELXTL.Version 5.10. Bruker AXS Inc., Madison, Wisconsin, USA.

Sheldrick G. M. (1999).SADABS. Version 2.01. Bruker AXS Inc., Madison, Wisconsin, USA.

Tracy, J. W., Gregory, N. W. & Lingafelter, E. C. (1962).Acta Cryst.15, 672±674.

Figure 1

supporting information

sup-1

supporting information

Acta Cryst. (2001). E57, m80–m81 [doi:10.1107/S1600536801001660]

Solvated CrBr

(thf)

, a linear chain in the solid state

Brendan Twamley, Ralph Zehnder and Pamela J. Shapiro

S1. Comment

(THF)2CrBr2, (I), bears a close resemblance to the parent compound CrBr2 (Tracy et al., 1962). Both show slightly

distorted octahedral coordination and both have similar in-plane Cr—Br bond distances, 2.5825 (5) Å in (I) and 2.545 (1)

Å in CrBr2. The solvent molecule, THF in this case, occupies an in-plane coordination site with a Cr—O distance of

2.072 (3) Å. The solvent molecule is coordinated orthogonally to the Cr—Br vector with an angle of 90.009 (8)°. The

THF molecule is in a half-chair conformation with a total puckering amplitude of QT = 0.363 Å (Cremer & Pople, 1975).

The orientation of the THF molecule is influenced by the intramolecular interactions C4—H4a···Br1 and C1—H1a···Br1i

(see Table 1) which tilt the ring towards each Br atom. The out-of-plane coordination site is occupied with an

intermolecular Cr1···Br1ii _{interaction of 2.9874 (5) Å [symmetry code: (ii) 1 + x, y, z]. The corresponding interaction in}

CrBr2 has a Cr···Br distance of 2.998 (1) Å. The distortion from ideal octahedral geometry is also reflected in the Br1—

Cr1—Br1ii _{angle of 94.65 (2)°. With the THF molecules occupying the other coordination sites, (I) can only form a}

staggered chain instead of the planar sheets found in CrBr2. In this case, the direction of propagation is along [100] (Fig.

1). Other solvent coordinated CrII_Br

2 species that are octahedrally coordinated show a wide range of Cr—Br distances.

The complex CrBr2(CH3CN)2 (Halepoto et al., 1990), which also forms linear chains, has an in-plane Cr—Br distance of

2.545 Å and an out-of-plane distance of 2.976 (1) Å. However, the molecular species trans-CrBr2(pyridine)4 (Holah et al.,

1998) has a Cr—Br bond distance of 2.998 (1) Å which indicates a very weakly associated Br atom.

S2. Experimental

(THF)2CrBr2 was synthesized as a side product during the attempted synthesis of a chromocene bromide.

Tetramethyl-ethylenediyl(η5_{-biscyclopentadienyl)chromocene}II _{carbonyl (331 mg, 1.1 mmol) was reacted with}

1-bromo-2-methyl-propane (155 mg, 1.1 mmol) in THF for 20 h at 378 K, with no color change. Dibromomethane (excess) was then added

to increase the bromide concentration. Excess solvent and reagents were removed under reduced pressure and the green

residue redissolved in THF (20 ml) and filtered. The resulting solution was concentrated to promote crystallization and

cooled in a 278 K refrigerator overnight. The supernatant was decanted yielding a green crystalline product. The

supernatant was concentrated under reduced pressure to yield a fine pale green powder. Combined yield 68 mg, 19.1%,

Figure 1

Packing diagram of (I) showing the staggered propagation along the [100] direction. H atoms have been omitted for

clarity.

dibromobis(tetrahydrofuran-O)chromium(II)

Crystal data

[CrBr2(C4H8O)2]

Mr = 356.03

Triclinic, P1

a = 4.1043 (7) Å

b = 7.4530 (13) Å

c = 9.2875 (16) Å

α = 87.777 (3)°

β = 78.619 (3)°

γ = 87.281 (3)°

V = 278.07 (8) Å3

Z = 1

F(000) = 174

Dx = 2.126 Mg m−3

Mo Kα radiation, λ = 0.71073 Å Cell parameters from 839 reflections

supporting information

sup-3

µ = 8.18 mm−1

T = 203 K

Plate, pale yellow 0.25 × 0.20 × 0.15 mm

Data collection

Siemens SMART 1000 diffractometer

Radiation source: normal-focus sealed tube Graphite monochromator

Detector resolution: 8.3 pixels mm-1

ω scans

Absorption correction: empirical (using intensity measurements)

(SADABS; Sheldrick, 1999)

Tmin = 0.184, Tmax = 0.293 2917 measured reflections 962 independent reflections 897 reflections with I > 2σ(I)

Rint = 0.029

θmax = 25.0°, θmin = 2.2°

h = −4→4

k = −8→8

l = −11→11

Refinement

Refinement on F2 Least-squares matrix: full

R[F2 _{> 2σ(F}2_{)] = 0.027}

wR(F2_{) = 0.071}

S = 1.08 962 reflections 61 parameters 0 restraints

Primary atom site location: structure-invariant direct methods

Secondary atom site location: difference Fourier map

Hydrogen site location: inferred from neighbouring sites

H-atom parameters constrained

w = 1/[σ2_(F

o2) + (0.0436P)2 + 0.1523P] where P = (Fo2 + 2Fc2)/3

(Δ/σ)max = 0.001 Δρmax = 0.58 e Å−3 Δρmin = −0.70 e Å−3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 _{against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F}2_, conventional R-factors R are based on F, with F set to zero for negative F2_{. The threshold expression of F}2 _{> σ(F}2_{) is used} only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2₎

x y z Uiso*/Ueq

Br1 0.10559 (9) 0.70378 (5) 0.37413 (4) 0.02022 (17)

Cr1 0.5000 0.5000 0.5000 0.0180 (2)

O1 0.4032 (7) 0.6622 (3) 0.6810 (3) 0.0245 (6)

C1 0.2743 (10) 0.5980 (5) 0.8298 (4) 0.0242 (9)

H1A 0.3974 0.4886 0.8536 0.029*

H1B 0.0382 0.5724 0.8425 0.029*

C3 0.2812 (11) 0.9167 (5) 0.8283 (4) 0.0244 (9)

H3A 0.0454 0.9507 0.8342 0.029*

H3B 0.3948 1.0190 0.8558 0.029*

C2 0.3237 (10) 0.7515 (5) 0.9266 (4) 0.0240 (9)

H2A 0.5459 0.7433 0.9508 0.029*

H2B 0.1558 0.7528 1.0177 0.029*

H4A 0.3266 0.9144 0.6022 0.028*

H4B 0.6753 0.8848 0.6524 0.028*

Atomic displacement parameters (Å2₎

U11 _U22 _U33 _U12 _U13 _U23

Br1 0.0210 (2) 0.0198 (2) 0.0199 (3) 0.00074 (15) −0.00461 (16) 0.00071 (15)

Cr1 0.0230 (5) 0.0167 (4) 0.0144 (5) 0.0034 (3) −0.0046 (4) −0.0026 (3)

O1 0.0390 (16) 0.0173 (13) 0.0152 (14) −0.0007 (12) −0.0004 (12) −0.0019 (11)

C1 0.029 (2) 0.022 (2) 0.018 (2) 0.0006 (16) 0.0015 (17) −0.0007 (16)

C3 0.027 (2) 0.024 (2) 0.021 (2) 0.0004 (16) −0.0020 (17) −0.0058 (16)

C2 0.028 (2) 0.027 (2) 0.017 (2) 0.0021 (17) −0.0026 (17) −0.0052 (17)

C4 0.032 (2) 0.0162 (19) 0.021 (2) −0.0041 (16) −0.0036 (17) −0.0010 (15)

Geometric parameters (Å, º)

Br1—Cr1 2.5825 (5) O1—C4 1.458 (4)

Cr1—O1i _{2.072 (3) C1—C2 1.527 (6)}

Cr1—O1 2.072 (3) C3—C4 1.512 (5)

Cr1—Br1i _{2.5825 (5) C3—C2 1.528 (6)}

O1—C1 1.450 (5)

O1i_{—Cr1—O1 180.00 (9) C1—O1—Cr1 124.1 (2)}

O1i_—Cr1—Br1i _{90.09 (8) C4—O1—Cr1 125.1 (2)}

O1—Cr1—Br1i _{89.91 (8) O1—C1—C2 104.7 (3)}

O1i_{—Cr1—Br1 89.91 (8) C4—C3—C2 103.6 (3)}

O1—Cr1—Br1 90.09 (8) C1—C2—C3 102.1 (3)

Br1i_{—Cr1—Br1 180.0 O1—C4—C3 105.2 (3)}

C1—O1—C4 110.7 (3)

Symmetry code: (i) −x+1, −y+1, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A D—H H···A D···A D—H···A

C4—H4A···Br1 0.98 2.99 3.599 (4) 122

C1—H1A···Br1i _{0.98 2.99 3.607 (4) 122}